The present invention is directed to infinitely variable transmissions and methods and apparatus for control of infinitely variable transmissions. More particularly, the present invention is directed to an infinitely variable transmission using a walking beam with a variable fulcrum and to methods and apparatuses for controlling infinitely variable transmissions in response to predetermined parameters of an internal combustion engine, such as manifold pressure.
For nearly every application where a prime mover or power source is coupled to an output device, a transmission device is required therebetween to convert the output motion of the prime mover to a form usable by the driven device. For some applications, a fixed, single speed transmission is suitable. However, for most applications, particularly for applications involving motor vehicles, multiple discrete transmission ratios are provided in order to enhance the efficiency of the prime mover while providing optimum torque or fuel economy over a wide range of speeds. However, the use of multiple discrete gear ratios in a transmission has several well known drawbacks, including a loss of power and efficiency while shifting between gear ratios. Furthermore, discretely variable transmissions, while more efficient than single speed transmissions, are still limited in their ability to efficiently couple a prime mover with a driven device.
For this reason, many continuously or infinitely variable transmissions have been designed in the past in order to overcome the disadvantages of discretely variable transmissions. These devices have taken various forms including belt driven transmissions, gear driven transmissions, and walking beams having variable fulcrums. While many continuously variable transmissions of the belt-type have been offered commercially in the past, such devices have had limited commercial success in the past, due partially to a loss of efficiency resulting from belt slippage, the cost, weight and space requirements of such tranmissions, and the slow responsiveness of such transmissions to changing conditions.
An example of a power transmission device of the variable fulcrum walking beam type is disclosed in U.S. Pat. No. 982,666, to Girin. Girin teaches a change speed gear having a driving and a driven shaft, a lever connected to the driving shaft and a clutch mechanism engaging the driven shaft and connected to the other end of the lever. A movable fulcrum is provided intermediate the two ends of the lever. The fulcrum is displaced to vary the ratio between the rotational speed of the drive shaft to the driven shaft. Girin, however, uses a complicated and space consuming series of cranks to transfer power to and from the lever. Furthermore, Girin nowhere provides for an automatic means controlling the position of the fulcrum. Additionally, the device in Girin is intended to permit selection of the output speed by movement of the fulcrum point, while permitting the motor to run at any predetermined speed. Thus, no effort is made in Girin to optimize fuel efficiency or torque. Girin nowhere suggests that a walking beam and movable fulcrum arrangement may be advantageously used to control output characteristics in a cooperative manner with a prime mover supplying a controllably varied output. Instead, the device is only used to directly control output speed independent of the functioning of the prime mover.
It has occurred to the Applicant in the present application that a variable fulcrum walking beam may be advantageously used to achieve improvements in fuel efficiency in fossil fuel combustion engines. This is particularly true if appropriate controls are provided to optimize the transmission ratio in response to conditions in the prime mover, and possibly in response to additional input supplied by other devices used in conjunction with the internal combustion engine and from the human operator of the internal combustion engine. Such a device would be particularly useful in a motor vehicle in order to improve the fuel efficiency of the internal combustion engine of the motor vehicle. However, in order to be satisfactory for use in a motor vehicle, such a device must be made in a compact, lightweight and inexpensive form and must be capable of smoothly and efficiently delivering power from an internal combustion engine to the wheels of a motor vehicle.
The need for a fuel efficient transmission for motor vehicles has increased recently as a result of the dramatic increase which has occurred in the cost of fuel, as well as the imminent shortage of fuel which is being predicted by many independent sources. Thus, an efficient and lightweight infinitely variable transmission is needed. Furthermore, as a result of the need to conserve fuel, the internal combustion engines in motor vehicles have become smaller and smaller and, accordingly, the output of internal combustion engines in typical vehicles has decreased. While various modifications to the internal combustion engine itself have been made to permit an increase in the amount of torque and power available from a particular engine, many of the vehicles still have undesirably sluggish performance as a result of the downsized engines. The dual problems of increased fuel prices and sluggish performance have resulted in a reversal of the previous trend away from manual transmissions to automatic transmissions.
Accordingly, it is highly desirable to provide an automatic infinintely variable transmission which provides sufficient torque to overcome the sluggishness problem of current motor vehicles using discrete automatic transmissions. What is also needed is a method and apparatus for directly controlling an infinitely or continuously variable transmission for a motor vehicle in response to vehicle and, possibly, operator inputs so as to optimize the operation of the internal combustion engine of the vehicle under varying conditions.